1. Field of the Invention
The present invention relates to a substrate transport apparatus and a substrate transport method. Exemplary substrates to be transported include semiconductor wafers, glass substrates for liquid crystal display devices, glass substrates for plasma display devices, substrates for optical disks, substrates for magnetic disks, substrates for magneto-optical disks, and substrates for photo masks.
2. Description of Related Art
Substrate treatment apparatuses of a single substrate treatment type for use in a semiconductor device production process typically include an indexer section and a treatment section. The treatment section includes a treatment unit for treating a substrate, and a main transport robot which loads and unloads the substrate with respect to the treatment unit (see, for example, U.S. Patent Application Publication No. US2002/0150459A1). The indexer section includes a carrier retaining portion for retaining a carrier which is capable of accommodating a plurality of substrates in a stacked state, and an indexer robot which transports a substrate between the carrier retained by the carrier retaining portion and the main transport robot.
An untreated substrate is taken out of the carrier and transferred to the main transport robot by the indexer robot, and loaded into the treatment unit by the main transport robot. A substrate treated by the treatment unit is unloaded from the treatment unit and transferred to the indexer robot by the main transport robot, and carried into the carrier by the indexer robot.
The main transport robot and the indexer robot are, for example, of a double arm type, each including an upper hand and a lower hand vertically arranged in a retractable manner and adapted to hold the treated substrate by the upper hand thereof and hold the untreated substrate by the lower hand thereof. That is, the main transport robot loads the untreated substrate into the treatment unit by the lower hand thereof immediately after unloading the treated substrate from the treatment unit by the upper hand thereof. Further, the main transport robot transfers the treated substrate from the upper hand thereof to the upper hand of the indexer robot, and receives another untreated substrate from the lower hand of the indexer robot by the lower hand thereof. The indexer robot transports the treated substrate to the carrier and carries the treated substrate into the carrier by the upper hand thereof, and takes out another untreated substrate from the carrier by the lower hand thereof.
The substrates are transferred between the main transport robot and the indexer robot in the following manner.
1. The indexer robot is moved to a position opposed to a substrate transfer position.
2. The indexer robot advances the lower hand thereof holding the untreated substrate to the substrate transfer position.
3. The main transport robot is moved to a position opposed to the substrate transfer position.
4. The main transport robot advances the lower hand thereof to the substrate transfer position, slightly moves up the lower hand thereof to take up the untreated substrate from the lower hand of the indexer robot, and then retracts the lower hand thereof.
5. The indexer robot retracts the lower hand thereof.
6. The indexer robot advances the upper hand thereof to the substrate transfer position.
7. The main transport robot advances the upper hand thereof holding the treated substrate to the substrate transfer position, slightly moves down the upper hand thereof to transfer the treated substrate to the upper hand of the indexer robot, and then retracts the upper hand thereof.
8. The indexer robot retracts the upper hand thereof.
With the aforesaid arrangement, the main transport robot requires time for the advancement and retraction of the upper and lower hands thereof and for the upward and downward movement of the upper and lower hands thereof for the transfer of the substrates between the main transport robot and the indexer robot. Further, the indexer robot requires time for the advancement and retraction of the upper and lower hands thereof.
Therefore, the main transport robot and the indexer robot are constrained for a longer period for the transfer of the substrates therebetween, thereby hindering the improvement of the substrate transport speed and the reduction of the substrate transport time.